1. Field of the Invention
The present invention relates to a liquid medicine continuous infuser for giving a liquid medicine to a patient over a long time. More particularly, it relates to a liquid medicine continuous infuser for flowing out a liquid medicine by utilizing a pressing pressure of an elastic bag (balloon).
2. Description of the Related Art
For giving liquid medicine to a patient such as an adult whose physical strength is exhausted, liquid medication systems take many hours to match the physical strength condition of the patient in treating the disease. Such liquid medicine may include, for example, an anticancer drug, an anodyne, a local anesthetic, a blood sugar level adjuster, etc. Each of these liquid medicines is delivered to a patient through a vein, an artery, a subcutaneous tissue, or by use of an epidural injection.
As one of such liquid medication systems, there has been disclosed a liquid medicine continuous infuser or a fountain syringe for continuously flowing out a liquid medicine by utilizing the pressing pressure of a balloon, as disclosed in Japanese Patent Application Laid-Open No. 64-70069. This liquid medicine continuous infuser comprises a cylindrical external axis, an internal axis slidably accommodated within this external axis and a cylindrical balloon with its both ends fixed air-tight at an outer periphery of these axes. A flow rate controller, a tube, a liquid medicine injecting needle, etc. are connected sequentially to an opening of the external axis through a three-directional stop cock.
A liquid medicine to be given to a patient is filled into the balloon through the three-directional stop cock, the external axis and a gap between the external axis and the internal axis. The liquid medicine is then passed through the flow rate controller, the tube, the adapter, etc. after having been switched over by the three-directional stop cock. Finally the liquid medicine is delivered to the patient through a vein or other route by a liquid medicine injecting needle. At the time of charging the liquid medicine into the balloon, the internal axis is projected from the external axis along with the charging of the liquid medicine. Thus, the capacity of the balloon can be made larger by inflating the balloon not only in a radial direction but also in an axial direction. Also, at the time of finishing the medication of the liquid medicine, the internal axis is accommodated within the external axis and the balloon is contracted into an axial direction, so that a remaining volume of the liquid medicine can be made smaller.
It is desirable that the volume of the liquid medicine remaining in the liquid medicine continuous infuser after finishing the medication is as small as possible to ensure a secure medication and avoiding an occurrence of unused liquid medicine. However, the liquid medicine continuous infuser having the above-described structure cannot meet the above requirement satisfactorily. Thus it is desired to provide a novel liquid medicine continuous infuser that can effectively reduce the volume of the liquid medicine remaining in the infuser after finishing a medication.
Further, from the viewpoint of achieving proper medication, it has also been desired to provide a liquid medicine continuous infuser that can maintain a substantially constant level of a liquid medicine given to a patient without a sudden variation in the volume of the liquid medicine during medication.